Hmm rough running engine...

[Georgio]

Had my Z4 for a couple of years now, zero problems, starts first time every time etc. and with only 60k on the clock it's as sweet as a nut.
Then this morning go out and on the way back the engine starts to run rough like no power and sounds like there's a hole in the exhaust.
So I make it back home and stick in the OBD reader and it's saying PO366 fault which is the timing belt sensor, as it's been so wet I spray the sensors with WD40 just incase some moisture has got in there, clear the fault then try and start the engine.
Turns over ok but doesn't want to fire.
A quick look on the internet and I see various problems associated with this one of which highlights a collapsed timing chain tensioner which causes the timing belt to jump a couple of sprockets. Ok now I'm worried as I know the consequences of the timing chain not doing it's job.
One sure fire way is to look through the oil flap and try and move the timing chain by push/pulling it which should be minimal movement that close to the sprocket and of course mine is as slack as you like...

 

[Smartbear]

Had my Z4 for a couple of years now, zero problems, starts first time every time etc. and with only 60k on the clock it's as sweet as a nut.
Then this morning go out and on the way back the engine starts to run rough like no power and sounds like there's a hole in the exhaust.
So I make it back home and stick in the OBD reader and it's saying PO366 fault which is the timing belt sensor, as it's been so wet I spray the sensors with WD40 just incase some moisture has got in there, clear the fault then try and start the engine.
Turns over ok but doesn't want to fire.
A quick look on the internet and I see various problems associated with this one of which highlights a collapsed timing chain tensioner which causes the timing belt to jump a couple of sprockets. Ok now I'm worried as I know the consequences of the timing chain not doing it's job.
One sure fire way is to look through the oil flap and try and move the timing chain by push/pulling it which should be minimal movement that close to the sprocket and of course mine is as slack as you like...

Hmm, not 100% sure but are you sure the tensioner isn't activated by oil pressure? If that's the case it should tighten when the engine starts.
Did it make a terrible rattle when it was running?
Regards

 

[Georgio]

Nope, no rattle at all, just running rough like it was in limp mode but with no mil light. I hope you're right about the tensioner only working under oil pressure.
Still getting it into a garage tomorrow hopefully and seewhat they reckon, hopefully it's something easily fixed.

 

[swanicyouth]

What year and engine?

No E85/6 has a timing belt.


It's very odd to have a hard code set for an engine management issue - but no MIL. Was it a P (pending) code (usually preceded by a P on most scanners)?

If it's a P code - that would explain no MIL - and then your issue is likely not related to that code. It's not uncommon for the crankshaft or camshaft position sensors to go bad - leaving you with a rough running car. However, I believe as long as one of them is working the car will still run.

You can tell if the timing chain jumped by doing a compression test.

 

[Smartbear]

What year and engine?

No E85/6 has a timing belt.


Sent from my iPhone using Tapatalk

He knows it has a chain as he's checked the tension of it, just called it a belt by mistake I think.
Regards

 

[Georgio]

Yea sorry I meant chain not belt. Googling the code thrown up which was PO366 it seems to be quite a common fault especially for 3 series and the crank sensor.
I suppose part of the cleavat we have for having more efficient, powerful yet frugal engines is to have sensors all over the shop any one of which could fail, still can't complain, it's the first thing to go wrong in two years unlike other forum members that have had nothing but grief from day one.

 

[Stratts]

If you mean the crank sensor then the symptoms are often difficulty starting and sluggish performance, especially at lower revs, and you'll find you need a lot of throttle to make any progress.

Not sure where the sensor is on your engine, but failure will not always throw a warning light as it's not that type of fault. Plenty of other things it can be of course, but I've had these sensors go before and it's more of an annoyance than anything. The noise my old cars used to make when they were firing up sounded like grinding metal.

If you need new sensors, always get OEM or equivalent. The cheap stuff will fail in short time.

 

[Georgio]

Well the garage have replaced the crankshaft sensors...and nothing, still won't fire. They're now suggesting that the crank chain could have stretched, surely you wouldn't get that at 60k?
My gut feeling is that the tensioner has collapsed cusing the sprocket teeth to jump throwing out the timing.

 

[fixit man]

Hi, found this link....http://www.bmwland.co.uk/forums/viewtopic.php?f=23&t=124406
Seems identical to your problem, turned out to be the tensioner !

 

[Georgio]

Hi, found this link....http://www.bmwland.co.uk/forums/viewtopic.php?f=23&t=124406
Seems identical to your problem, turned out to be the tensioner !

Yep garage had the car for a few days and it was the plastic chain guide that had broken up allowing the chain to skip a few teeth. Should be picking the car up today so will be interesting to see the difference.
My car has 60k on the clock so I would urge anyone who notices any strange noises on startup/turn off to get this plastic guide checked as it seems to be quite a common problem.
I didn't notice anything in the case of my car, but I'm expecting a bill around the grand mark. If I'd known about this issue I would have got the guide replaced before it failed.

The question is, why are BMW using plastic in such a crucial part inside the engine when it's so well documented that it's bound to fail...

 

[Smartbear]

It could be a metallergy problem if the chain runs on it, using metal might wear the cam chain very badly-glad you've got the problem sorted out.
Regards